Year	Years
1970	1.78
1971	1.83
1972	1.89
1973	1.95
1974	2.01
1975	2.07
1976	2.13
1977	2.2
1978	2.26
1979	2.33
1980	2.4
1981	2.47
1982	2.54
1983	2.62
1984	2.7
1985	2.78
1986	2.86
1987	2.94
1988	3.02
1989	3.11
1990	3.2
1991	3.29
1992	3.38
1993	3.48
1994	3.57
1995	3.67
1996	3.78
1997	3.88
1998	3.99
1999	4.1
2000	4.21
2001	4.32
2002	4.44
2003	4.56
2004	4.68
2005	4.8
2006	4.93
2007	5.05
2008	5.18
2009	5.31
2010	5.45
2011	5.58
2012	5.72
2013	5.86
2014	6
2015	6.14